Because of their relatively high energy density and slow loss of charge over time when not in use, compared to typical rechargeable batteries, lithium-ion batteries have become increasingly popular for use in consumer electronics and for other applications, including defense, aerospace, and automotive (e.g., electric and hybrid cars). Although lithium-ion batteries work relatively well for a variety of applications, the batteries can exhibit shortened life and reduced cycle efficiency as the batteries are discharged and recharged, particularly when lithium is used as the anode material.
A lithium-ion battery generally includes one or more electrochemical cells, wherein each electrochemical cell includes an anode, a cathode, an electrolyte, and a separator between the anode and the cathode. During discharge of the battery, lithium ions carry current from an anode to a cathode and through an electrolyte and a separator of the electrochemical cell. To recharge the battery, an external current source of sufficient bias is applied to the battery to cause the lithium ions to flow in a reverse direction—from the cathode to the anode and to redeposit on the anode.
Lithium-ion electrochemical cells may use a variety of materials, such as carbon, as an anode. However, lithium metal may be particularly attractive for use as the anode of electrochemical cells because of its extremely light weight and high energy density, compared, for example, to anodes, such as lithium intercalated carbon anodes, where the presence of non-electroactive materials increases weight and volume of the anode, and thereby reduces the energy density of the cells. These features are highly desirable for batteries for portable electronic devices such as cellular phones and laptop computers, as well as electric vehicles, military, and aerospace applications, where low weight is important.
Unfortunately, when lithium metal is used as an anode in lithium-ion batteries, progressive formation of finely dispersed, high surface area lithium may occur at the anode surface after repeated charging and discharging of the cell. The high surface area lithium is very reactive and can react with electrolyte components or become electrically isolated from the bulk anode material, which in turn can adversely affect the cycle efficiency and life of the lithium-ion electrochemical cell.
Accordingly, improved lithium-ion cells having a lithium anode, components of the cells, batteries including the cells, and method of forming and using the cells are desired.